1. Field of the Invention
The disclosure relates to a circuit board capable of preventing contact of a gold finger and solder, and more specifically, to a circuit board having a substrate whereon a sunken portion is formed for accommodating a gold finger structure, so as to prevent contact of the gold finger and solder.
2. Description of the Prior Art
A circuit board with a gold finger structure is widely utilized in electronic products, such as a mobile phone, a PDA, a computer, and so on. However, the electrical function will be affected as the gold finger structure is stained with solder, due to insulating oxidation generated by electrochemistry reaction of stannum with higher activity, resulting in affecting signal transmission. Hence, the gold finger structure is prevented from contacting with the solder. In general, a pad and the gold finger structure of the conventional circuit board are on the same horizontal level. After stencil printing or wiping the stencil, the solder is often left beside a hole or on a bottom of the stencil, so that the solder will be stained on the gold finger structure of the next circuit board after the next circuit board contacts with the stencil. Then the solder stained on the gold finger structure is heated and hardened, leading to affection of the electrical function.
There are several ways for solving the above-mentioned problem. The stencil can be wiped more frequently or by other wiping operation, such as wet wipe, dry wipe or vacuum wipe, but it increases cycle time of production and manufacture cost. Besides, a size of the hole on the stencil can be reduced for preventing the solder powder from bouncing outwardly, but it reduces the soldering efficiency. In addition, a solder mask type can be adhered to the gold finger structure during the stencil printing, but it not only increases labor hours and cost of the solder mask type but also remains adhesive on the gold finger structure. Therefore, there is a need to find a solution to prevent the solder from staining on the gold finger structure with low manufacture cost and high production yield.